Ptcx09

I highly recommend the Yoga 730, I was able to pick it up on sale for $579 at best buy a few months ago. Though, you may still be able to find it elsewhere (Newegg,Amazon etc) for around that price. I dont recommend the Surface, I support them at work, the Surface Pro 7 (latest iteration) is not upgrade-able, so you'll likely be over your budget if you were to get a custom built one. The only Surface devices that can be upgraded are the X and Laptop 3, of which i believe you can only upgrade the SSD, and regardless would be out of your budget to start with.

Ive used these before, they work really well. Use a pair of pliers to pull the two stems: https://www.amazon.com/Cosmos-Pieces-Rubber-Mounting-Screws/dp/B00H9905KA/ref=sr_1_4?crid=2IXT4SJZE45DW&keywords=case+fan+rubber+mounts&qid=1582742841&sprefix=case+fan+rub%2Caps%2C150&sr=8-4